The American model took to Instagram on Sunday to promote Bellissima Prosecco, the vegan and organic spirit backed by her, and looked stunning in a navy polka dot Alessandra Rich midi dress with button detailing and a white-collar, which retailed at the time at £1,750.
In the fun photo, the mother-of-three can be seen sitting on a chair whilst raising a glass of champagne. Her dress is not fully buttoned-up, leaving her perfect legs in full view.
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"Things to look forward to… SUNDAY BRUNCH with bubbly and friends @bellissimaprosecco #organicprosecco #vegan #organicgrapes and some of my wines are #zerosugar #zerocarbs," she captioned the sexy shot.
Christie's dress received an incredible amount of praise, with many questioning where it was from.
"I think it's by Alessandra Rich. It looks like one worn by the Duchess of Cambridge. It's gorgeous!" replied one, whilst a second added: "And @abigailspencer wore it to Meghan Markle's wedding."
Christie looked stunning in the same dress Kate Middleton owns
"GORGEOUS," remarked a third, whilst a fourth added: "Love that dress and those amazing [shoes]. Looking fabulous!"
Christie has opened up about her style in the past and made the surprising revelation that she will "suffer" and wear heels for photos, but she much prefers flats.
"I'm most comfortable in shoes flat and to the ground. I like to be able to move, but if I'm going to be photographed, I will suffer with the heels," she told footwearnews.com.
Of her style changing as she's gotten older, she told Vogue in 2017: "In my own wardrobe, I guess I try to balance that thing of body consciousness and comfort, because if things are body conscious but uncomfortable, it usually means they're too tight. You have to exude that certain sense of comfort.
"And also, too tight just starts to look like you're trying too hard. Then I think that as you get older you have to keep things simple. I think that I feel the best when I'm in an old pair of jeans and a cashmere sweater, jean shirts, and white button-down shirts. Those elements stay relaxed and easy.
"A young girl can wear a Chanel bouclé jacket, for instance, and it looks great on her. But I feel like at my age, if I put on a Chanel jacket, it would age me."